Support frames are known for use in mineral mine workings which are composed of hydraulic props connected between roof and floor-engaging structures and a goaf shield pivotably connected between the roof and floor engaging structures. To advance the frame from time to time, and to advance a scraper-chain conveyor of an associated mine installation, it is known to operate a shifting mechanism connected between the floor-engaging structure of the frame and the conveyor. The shifting mechanism can conveniently take the form of an hydraulic ram and a guide beam positioned in a space between a pair of skids or sills forming the floor-engaging structure. When the frame is being shifted, the props are relieved and the ram of the shifting mechanism is operated to draw up the frame towards the conveyor. The guide beam then ensures the sills of the frame do not deviate from the desired path.
Support frames of the above-mentioned kind are known in various designs. In support frames described in DE-3317801 and DE-3713887 the guide beam is made up from several parallel resilient bars guided on lugs of a trough in which the shifting ram is accommodated. The bars are disposed at some distance above the floor and are connected together with a head piece and linked therewith to the conveyor. Guide beams with a flat profile are also known.
To facilitate shifting of the frame on the floor of the working, it is known to use a device which partially raises the floor sills during the movement of the frame. The operation of this device enables the sills to be released if they have become embedded in the floor and facilitates the sliding of the sills over the floor. Support frames employing such lifting devices are known for example from U.S. Pat. No. 4568222 and DE 3625826.
In these frames, the guide beam connected to the conveyor lies in the space between the floor sills and forms an abutment for the lifting devices. Often the lifting devices are operated in direct dependence on the shifting ram and control of the sills independent of the shifting ram is not possible in this case. Furthermore, part of the structure of the shifting ram is needed to operate the lifting device.
U.S. patent application Ser. No. 07/744368 (DE-OS 4027087.4) describes a frame with a modified lifting device with which the floor sills or skids can be lifted by a separate unit or units quite independent of the ram. In this frame, the piston rod of the ram is connected to the end of the guide beam remote from the mineral face so that when the rod is retracted the conveyor is displaced and when the rod is extended the frame is shifted up.
An object of the invention is to provide an improved support frame in which the guide beam and the lifting device can be arranged in a compact efficient manner allowing the floor skids to be lifted in a controlled way with the forces transferred to the floor via the guide beam without tilting or jamming despite unevenness in the floor.